Big toe won't stay on ground in squat

Whenever I squat the big toe points up like a hitch hikers thumb, the pad under it doesn't touch the ground if I lift my arches. Especially if I bend my knee.

 

I'm asking you guys because there are some real geniuses here.

Most likely it's just a habit you've picked up.

 

Passively:

Hold the squat position and see if you can get your toe down. You can use your hands to help, or even put a light weight plate over the toe to keep it down.

 

Actively:

Imagine you are trying to pick a pencil with your toes while squatting.